Film perforation standard with rounded corners developed by Dubray and Howell in the 1920s – designed for improved film stability and reduced wear, became the standard for 35mm negative film stock used in professional motion picture production.
What is DH Perforation?
DH Perforation (Dubray-Howell) is a film perforation standard with characteristic rounded corners. Developed in the 1920s, DH became the standard perforation for 35mm camera negative due to its improved durability.
History
| Year | Development |
|---|---|
| 1924 | Dubray & Howell develop |
| 1930s | Industry adoption |
| 1953 | SMPTE standard |
| Today | Standard for 35mm negative |
Technical Specifications
| Parameter | Value |
|---|---|
| Height | 2.794 mm |
| Width | 1.981 mm |
| Pitch | 4.740 mm |
| Corners | Rounded (0.5 mm radius) |
| Shape | Rectangle with rounded corners |
Comparison: Perforation Types
| Type | Corners | Application |
|---|---|---|
| DH (Dubray-Howell) | Rounded | Camera Negative |
| BH (Bell & Howell) | Rounded | Release Prints |
| KS (Kodak Standard) | Square | Positive Prints |
| CS (Cinema Scope) | Rounded | Anamorphic |
Why Rounded Corners?
| Advantage | Explanation |
|---|---|
| Fewer Tears | No sharp corners |
| Longer Lifespan | Reduced wear |
| Better Transport | Less snagging |
| Pin Tolerance | Smoother engagement |
Areas of Application
| Area | Perforation Type |
|---|---|
| Camera Original | DH |
| Interpositive | DH or KS |
| Internegative | DH or KS |
| Release Print | BH or KS |
Film Gate Compatibility
| Camera Type | Perforation |
|---|---|
| Arriflex | DH/BH |
| Panavision | DH/BH |
| Mitchell | DH/BH |
| Aaton | DH |
Pin Registration
| Aspect | Description |
|---|---|
| Pilot Pins | Engage in perforation |
| Registration | Image stability |
| Precision | Critical for VFX |
| Wear | Rounded corners are gentler |
Problems with Incorrect Perforation
| Problem | Cause |
|---|---|
| Unstable Image | Incorrect pitch |
| Film Tears | Incompatible pins |
| Scratches | Faulty transport |
| Weave | Poor registration |
DH vs. BH in Detail
| Aspect | DH | BH |
|---|---|---|
| Pitch | 4.740 mm | 4.740 mm |
| Shape | Same | Same |
| Usage | Negative | Positive |
| Reason | Higher tolerance | Print standard |
Modern Relevance
| Context | Significance |
|---|---|
| Analog Revival | Relevant again |
| Film Scanning | Perforation as reference |
| Archive | Identification of old films |
| Restoration | Understanding necessary |
Film Scanners and Perforation
| Aspect | Description |
|---|---|
| Perf Detection | Scanner recognizes type |
| Transport | Adjustment needed |
| Registration | Pin-based or sprocketless |
Film Manufacturers and Standards
| Manufacturer | Standard |
|---|---|
| Kodak | DH for negative |
| Fujifilm | DH for negative |
| ORWO | DH available |
| Foma | On order |
Today
DH perforation remains the standard for 35mm camera negative. With the analog revival and continued use of film for high-end productions, this over 100-year-old system retains its relevance – a testament to thoughtful engineering.
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